The present invention relates to metallic porphyrin complexes and their use as catalysts for the oxidation of hydrocarbons.
Epoxides, and other compounds having an oxirane ring such as ethylene oxide, propylene oxide, epoxidized fatty acids and the like, are conventionally produced by indirect means from the corresponding monoolefinically unsaturated compounds. For example, oxirane compounds typically are prepared by reaction of an olefin with chlorine in alkaline medium (forming, e.g., epichlorohydrin) followed by reaction with base; reaction of an olefin with an organic hydroperoxide employing a Group V, VI or VII metal catalyst; or reaction of an olefin with a peracid (e.g., peracetic or perbenzoic acid). U.S. Pat. No. 4,356,311 discloses the epoxidation of olefins using a transition metal nitro complex and a thallium (III) compound, such as a thallium (III) carboxylate, as an "olefin activator" or cocatalyst.
Interest in hydrocarbon oxidation has stimulated a major effort to model the oxygen activation and transfer reactions characteristic of cytochrome P-450. See, F. P. Guengerich et al., Acc. Chem. Res., 17, pp. 9-16 (1984); R. E. White et al., Ann. Rev. Biochem., 49, pp. 315-356 (1980); V. Ullrich, Trop. Curr. Chem., 83, pp. 67-104 (1979); J. T. Groves, Adv. Inorg. Biochem., pp. 119-145 (1979); J. T. Groves et al., J. Am. chem. Soc., 101, pp. 1032-1033 (1979); J. T. Groves et al., J. Am. Chem. Soc., 102, pp. 6375 et seq., (1980); J. T. Groves et al., J. Am. Chem. Soc., 105, pp. 5786-5791 (1983); C. K. Chang et al., J. Am. Chem. Soc., 101, pp. 3413-3415 (1979); J. R. Lindsay Smith et al., J. Chem. Soc., Perkin Trans. 2, pp, 1009-1015 (1982); D. Dolphin et al., Inorg. Chim. Acta, 79, pp. 25-27 (1983); D. Mansuy et al., J. Chem. Soc., Chem. Commun., pp. 253-254 (1983); C. L. Hill et al., J. Org. Chem., 48, pp. 3277-3281 (1983); I. Tabushi et al., J. Am. Chem. Soc., 103, pp. 7371-7373 (1981); J. J. Ledon et al., J. Am. Chem. Soc., 103, pp. 3601-3603 (1981); M. W. Nee et al., J. Am. Chem. Soc., 104, pp. 6123-6125 (1982); and M.-E. De Carvalho et al.,
Tetrahedron Lett., 24, pp. 3621-3624 (1983). Model and enzymic studies have implicated the intermediacy of an oxoiron intermediate in the probable catalytic cycle. See, J. T. Groves et al., J. Am. Chem. Soc., 96, p. 5274 (1974); J. T. Groves et al., J. Am. Chem. Soc., 103, pp. 2884-2886 (1981); B. Boso et al., J. Chem. Phys., 79, pp. 1122-1126 (1983); F. Lichtenberger et al., Biochem. Biophys. Res. Commun., 70, pp. 939-946 (1976); and K. B. Sharpless et al., J. Am. Chem. Soc., 93, pp. 2316-2318 (1971). The stoichiometry of the reaction requires two electrons from an exogenous source. Thus, most of the model systems have employed peroxidic oxidants such as iodosylbenzene or hypochlorite. The reductive activation of dioxygen has been reported in several cases, but each requires the consumption of at least stoichiometric amounts of a reducing agent. See D. Mansuy et al., supra and I. Tabushi et al., supra. Clearly, the development of a practical catalyst for the epoxidation of hydrocarbons must achieve access to the reactive oxometal species without the need for a coreductant. We describe here the first such system.